Nitrogen plasma activation of cactus-like MnO2 grown on carbon cloth for high-mass loading asymmetric supercapacitors

The electrochemical performance of high theoretical capacitance MnO2 is usually restricted to low mass loading electrode due to the slower electron/ion diffusion kinetics in dense electrodes. Defect engineering has been supposed to an effective way to improve the capacitive performance of transition metal oxides. Herein, cactuslike structure MnO2 was grown on carbon cloth (CC) and treated with N2-plasma to obtain the N-MnO2 electrode with high mass loading of 12 mg cm-2. Benefiting from the hierarchical structure and rich oxygen vacancies, the as-prepared N-MnO2 electrode delivered a high mass specific capacitance of 443F g-1 and a high areal capacitance of 5320 mF cm-2. Furthermore, the N-MnO2 electrode released an excellent rate capability with 71.8% capacitance retention at 20 mA cm-2 as well as gratifying cycling life with 96 % capacitance retention after 8 000 cycles at 20 mA cm-2. Moreover, an asymmetrical supercapacitor device assembled by N-MnO2 and activated CC can achieve a high energy density of 0.56 mWh cm-2 (46 Wh kg- 1) at the power density of 5.14 mW cm-2 (420 W kg-1) with good cycle stability. Such facile N2-plasma treatment for defect engineering shows great potential in the rational design for advanced supercapacitor electrodes with high mass loading.

Automated summary

By utilizing N2-plasma treatment, a high mass loading N-MnO2 electrode was successfully prepared, showing excellent capacitive performance and cycling stability. Under 20 mA cm-2, it exhibited capacitance retention rates of 71.8% and 96% respectively.